This application is a 35 U.S.C. 371 National stage filing of PCT/JP/98/0160, filed Apr. 8,1998.
The present invention relates to a processing system, such as an etching system.
A prior art etching system is provided with an upper electrode and a susceptor serving as a lower electrode disposed opposite to each other in a processing chamber formed in an airtight processing vessel. When subjecting a workpiece to a predetermined etching process by this etching system, the workpiece is mounted on the susceptor, a predetermined process gas is supplied into the processing chamber and the workpiece is etched for the predetermined etching process by a plasma produced in the processing chamber by applying a predetermined radio frequency power across the upper electrode and the susceptor. The process gas is supplied through a gas supply pipe connected to gas sources, for example, into a space defined between the upper electrode and an upper electrode holding member holding the upper electrode, and then the process gas is discharged through a plurality of gas discharge holes formed in the upper electrode into the processing chamber.
Since a surface of the upper electrode facing the susceptor is exposed to the plasma, it is possible that an electric field is concentrated on the gas discharge holes, more specifically on the edges of the gas discharge holes on the side of the processing chamber, whereby the edges of the gas discharge holes are etched and particles are produced. If the particles adhere to the workpiece, the yield of the products of the etching system is reduced. A technique disclosed in, for example, JP-A No. 61-67922 inserts insulating members each provided with a through hole and formed of a ceramic material, such as alumina, or a fluorocarbon resin, such as Teflon in the gas discharge holes to prevent the concentration of an electric field on the gas discharge holes. The gas discharge holes are tapered toward the processing chamber, and the insulating members substantially tapered so as to conform with the tapered gas discharge holes are inserted downward from the upper end of the gas discharge holes in the gas discharge holes. The insulating members are fitted in the gas discharge holes so that the lower end surfaces thereof on the side of the processing chamber are flush with the surface of the upper electrode facing the susceptor. Thus, the insulating members are not caused to fall off the upper electrode toward the lower electrode by the pressure of the process gas, and prevent the concentration of an electric field on the gas discharge holes.
Since the insulating members are inserted in the gas discharge holes from the upper side of the upper electrode, the upper electrode needs to be removed from the processing vessel every time the insulating members are changed and hence the work for changing the insulating members takes much time, the operating time of the etching system is reduced accordingly, reducing the throughput of the etching system. Since the processing chamber is heated at a high temperature during the processing operation of the etching system, thermal stress is induced in the upper electrode. Consequently, the gas discharge holes and the insulating members are strained and, sometimes, the lower end surfaces of the insulating members on the side of the processing chamber are dislocated from a plane including the lower surface of the upper electrode facing the lower electrode.
Sometimes, the edges of the through holes of the insulating member on the side of the processing chamber are etched by the plasma produced in the processing chamber and particles are produced. Since the insulating members are made of alumina or a fluorocarbon resin, it is possible that particles of aluminum or the fluorocarbon resin are produced, and the particles adhere to the workpiece and exert adverse effects, such as the reduction of insulating strength, on the workpiece.
In a processing system provided with an upper electrode comprising an upper electrode member and a cooling plate placed on the upper electrode member, both the upper electrode member and the cooling plate are provided with a plurality of gas discharge holes. In this processing system, a plasma produced in a processing chamber flows through the gas discharge holes formed in the upper electrode member and the gas discharge holes of the cooling plate are damaged by the plasma.
The present invention has been made in view of the foregoing problems in the prior art processing systems and it is therefore an object of the present invention to provide a novel, improved processing system provided with insulating members capable of being easily attached and changed and of being easily and uniformly positioned.
The present invention is applied to a processing system comprising a processing vessel defining an airtight processing chamber, upper and lower electrodes disposed opposite to each other in the processing chamber, and constructed to supply a predetermined process gas through a plurality of gas discharge holes formed in the upper electrode into the processing chamber. According to a first aspect of the present invention, insulating members each provided with a through hole permitting a process gas to pass through are fitted in the gas discharge holes, respectively, from the side of the processing chamber. Since the insulating members are inserted and fitted in the gas discharge holes through the outlet ends (ends on the side of the processing chamber) of the gas discharge holes, the insulating members can easily be attached to the upper electrode and easily be changed.
According to a second aspect of the present invention, the insulating members are fitted in the gas discharge holes of the upper electrode so as to project from the lower surface of the upper electrode facing the lower electrode into the processing chamber. Since lower end parts of the insulating members project from the lower surface of the upper electrode facing the lower electrode, the edges of ends of the gas discharge holes on the side of the processing chamber are not exposed to the processing chamber. Consequently, the edges not exposed to the processing chamber are not etched by a plasma produced in the processing chamber for a processing operation.
According to a third aspect of the present invention, each of the insulating members is provided with a flange capable of covering the rim of an end of the gas discharge hole on the side of the processing chamber. When the insulating members are fitted in the gas discharge holes, respectively, the flanges cover the rims of the ends of the gas discharge holes on the side of the processing chamber. Therefore, the edges of the ends of the gas discharge holes on the side of the processing chamber are not exposed to a plasma produced in the processing chamber and will not be etched. Thus, the life of the upper electrode provided with the gas discharge holes can greatly be extended.
According to a fourth aspect of the present invention, each of the gas discharge holes is provided with a shoulder, each of the insulating members is provided with a step, and the insulating members are fitted in the gas discharge holes so that the insulating members are positioned in place in the gas discharge holes with the steps thereof resting on the shoulders of the corresponding gas discharge holes. Since the insulating members are pressed into the gas discharge holes so that the steps are pressed against the shoulders of the gas discharge holes, the insulating members can correctly be positioned. Consequently, all the insulating members can be positioned at desired positions in the gas discharge holes. Since the steps of the insulating members are in close contact with the shoulders of the gas discharge holes, the plasma is unable to leak into a gas supply passage connected to the gas discharge holes.
According to a fifth aspect of the present invention, at least a part of the sidewall of each of the gas discharge holes between the open end thereof on the side of the processing chamber and the shoulder thereof is finished by a plasma-proofing process, such as an anodic oxidation process if the upper electrode is formed of aluminum. Therefore, the sidewalls of the gas discharge holes are not etched even if the plasma infiltrates into gaps between the sidewalls of the gas discharge holes and the insulating members. Since a part of the sidewall of each gas discharge hole between the shoulder and the open end opening into the gas supply passage is not finished by the plasma-proofing process, the outer surfaces of the insulating members and the sidewalls of the corresponding gas discharge holes are in airtight contact with each other. Therefore, the insulating members will not come off the gas discharge holes even if the pressure of the gas acts on the insulating members.
According to a sixth aspect of the present invention, the length of the insulating members is shorter than that of the gas discharge holes. When each insulating member is fitted in the gas discharge hole, a space is formed between the insulating member fitted in the gas discharge hole and the gas supply passage. Therefore, an optimum conductance can be secured and the process gas can be discharged in a desired mode through the through holes of the insulating members into the processing chamber.
According to a seventh aspect of the present invention, at least a part of the through hole of each insulating member is substantially tapered so as to expand toward the processing chamber. Since any edge is not formed in the open end of through hole on the side of the processing chamber, the insulating members have improved plasma resistance, and insulating member changing period can greatly be extended. Since the parts of the through holes of the insulating members are tapered so as to expand toward the processing chamber, the process gas can uniformly be distributed over a workpiece placed in the processing chamber.
According to an eighth aspect of the present invention, the insulating members are formed of a resin, such as a poly (ether ether ketone) resin of the formula (1), such as PEEK PK-450 commercially available from Nippon Poripenko K.K. or PEEK PK-450G commercially available from The Polymer Corp., a polyimide resin of the formula (2), such as VESPEL SP-1 commercially available from DuPont, or a poly(ether imide) resin of the formula (3), such as ULTEM UL-1000 (natural grade) commercially available from Nippon Poripenko K.K. or The polymer Corp. 
The insulating members has an improved plasma resistance, insulating member changing period can greatly be extended, and influence on the workpiece can be limited to the least extent even if the insulating members are etched by the plasma.
According to a ninth aspect of the present invention, a processing system comprises: a processing vessel having an airtight processing chamber, an upper electrode disposed in an upper region of the processing chamber, and a lower electrode disposed below and opposite to the upper electrode in the processing chamber; wherein the upper electrode has an upper electrode member and a cooling plate disposed on the upper electrode member, the upper electrode member and the cooling plate are provided with a plurality of gas discharge holes through which a predetermined process gas is supplied into the processing chamber, and insulating members each provided with a through hole permitting the process gas to flow through are fitted in the gas discharge holes so as to cover the sidewalls of the gas discharge holes. Thus, it is possible to prevent the etching of the sidewalls of the gas discharge holes of the cooling plate by a plasma produced in the processing chamber.
According to a tenth aspect of the present invention, at least an end part of the through hole of each insulating member on the side of the processing chamber is substantially tapered so as to expand toward the processing chamber. The insulating members provided with the through holes having the substantially tapered parts, respectively, are not easily etched, and insulating member changing period can be extended.
According to an eleventh aspect of the present invention, each of the gas discharge holes of the cooling plate is provided with a shoulder, each of the insulating members is provided with a step, and the insulating members are fitted in the gas discharge holes so that the insulating members are positioned in place in the gas discharge holes with the steps thereof resting on the shoulders of the corresponding gas discharge holes. Since the insulating members are pressed into the gas discharge holes so that the steps are pressed against the shoulders of the gas discharge holes, the insulating members can correctly be positioned. Consequently, all the insulating members can be positioned at a desired position in the gas discharge holes of the cooling plate.
As mentioned above, according to the present invention, the insulating members are fitted in the gas discharge holes, respectively, of the upper electrode from the side of the outlet ends of the gas discharge holes (from the side of the processing chamber). Therefore, the insulating members can easily be attached to and removed from the upper electrode. Since the insulating members are positioned in place in the gas discharge holes with the steps thereof resting on the shoulders of the corresponding gas discharge holes, the insulating members can uniformly be disposed in the gas discharge holes. Since any edge is not formed in a part of each insulating member exposed to the atmosphere of the processing chamber and a part of the through hole of each insulating member is substantially tapered so as to expand toward the processing chamber, the insulating members are not easily etched and insulating member changing period can be extended. The insulating members formed of a predetermined resin have improved plasma resistance and extend insulating member changing period. Since a part of each of the sidewalls of the gas discharge holes between the open end thereof on the side of the processing chamber and the shoulder thereof is finished by a plasma-proofing process, and edges of the open ends of the gas discharge holes on the side of the processing chamber are covered with the insulating members, the life of the upper electrode can be extended.